1. Field of the Invention
The invention relates to a four-wheel drive vehicle and, more particularly, to a control system for a four-wheel drive vehicle including an automatic transmission and a disconnect mechanism, the automatic transmission being provided in a power transmission path between an engine and both main drive wheels and auxiliary drive wheels, the disconnect mechanism being provided in a power transmission path between the automatic transmission and the auxiliary drive wheels and configured to selectively connect or interrupt the power transmission path.
2. Description of Related Art
There has been suggested a four-wheel drive vehicle including an engine, main drive wheels, auxiliary drive wheels, an automatic transmission and a disconnect mechanism. Power is transmitted from the engine to the main drive wheels while the vehicle is traveling in a two-wheel drive mode or in a four-wheel drive mode. Power is transmitted from the engine to the auxiliary drive wheels while the vehicle is traveling in the four-wheel drive mode. The automatic transmission is provided in a power transmission path between the engine and both the main drive wheels and the auxiliary drive wheels. The disconnect mechanism is provided in a power transmission path between the automatic transmission and the auxiliary drive wheels, and disconnects a predetermined rotating element from the engine and the auxiliary drive wheels while the vehicle is traveling in the two-wheel drive mode. The predetermined rotating element is used to transmit power to the auxiliary drive wheels while the vehicle is traveling in the four-wheel drive mode. In the thus configured four-wheel drive vehicle, the disconnect mechanism is released to interrupt transmission of power from the engine and the auxiliary drive wheels to the predetermined rotating element while the vehicle is traveling in the two-wheel drive mode. Thus, co-rotation of the predetermined rotating element is suppressed while the vehicle is traveling in the two-wheel drive mode, so running resistance decreases, and fuel efficiency improves.